let it touch the metal box while it is touching the metal contacts that hold the fuse.

Pro tip #2: if you do let it touch and you get a big spark/bang, don't go sticking that screw driver back in there willy-nilly on the assumption that since the main fuse just blew there can't be any more electricity in the box now.

Don't ask me how I know this.

Actually, it is as easy as everyone else said it is. There are just a few precautions you will want to take.